1. Field of the Invention
The present invention relates to a method for fabricating a continuous vapor grown carbon fiber, a continuous vapor grown carbon fiber fabricated by the above-mentioned method, and applications thereof.
2. Description of the Related Art
Various heat elimination problems obstruct the development of electronic technology. In order to promote the functions and speed of accurate processors and graphic elements, it is necessary to elevate their power; however, the increasing power and reducing volume of products make the heat elimination of them a rigorous challenge. There are more or less heat elimination problems in IC, memory, LED and the like, and one of the solutions is using a substrate having high conductivity. For example, one ordinary personal computer has a sufficient space to eliminate heat by forced convection, but an article comprising a LED cannot eliminate heat by the same way; therefore, the use of a substrate having high conductivity will be important in the heat management of said article. But, most conventional materials having high conductivity are metals whose conductivity is limited and cannot response the needs of the heat management in this industry for future. Since then, composite materials having higher conductivity is under development. In those composite materials used for eliminating heat, the most popular reinforced material is carbon fiber. There are various carbon fibers, and the one having highest conductivity is the vapor grown carbon fiber. The density of the vapor grown carbon fiber is ¼ or less than that of copper, and the room temperature thermal conductivity of a graphitized vapor grown carbon fiber is at most 1950 W/m-K which is approximately five times higher than that of copper. Moreover, the resistance of the vapor grown carbon fiber is extreme low, i.e. about 0.6 μΩ·m, which is similar to that of titanium. The vapor grown carbon fiber has the best conductivity and resistance, and it also has good tensile stress and stretching coefficient; therefore, the vapor grown carbon fiber is excellent for developing composite materials having high conductivity.
The traditional vapor grown carbon fibers are short fibers having a length of at most hundreds micrometers, so the composite materials fabricated by these short fibers have lots of discontinuity, which restrict the conductivity of heat, and thereby the conductivity of these composite materials is merely equal to or lower than that of aluminum. In other words, although the vapor grown carbon fiber has a thermal conductivity of as high as 1950 W/m-K, but the composite materials fabricated by discontinuous short fibers do not have the expected heat elimination effect. In order to make the composite materials have the advantageous high conductivity from vapor grown carbon fibers, it is necessary to increase the length of them. Thus, the method for developing a vapor grown carbon fiber having a continuous structure and a length to be increased dramatically is a very important issue.